The present invention relates to novel 3,7,9,9-tetrasubstituted 3,7-diazabicyclo[3.3.1]nonane compounds which bear a substituted phenyl radical in position 3, and to their salts and to pharmaceutical preparations containing these compounds and to processes for the preparation of these compounds and to the use of these compounds for inhibiting cardiac arrhythmia in mammals.
3-Benzoyl-3,7-diazabicyclo[3.3.1]nonane derivatives with antiarrhythmic properties are already known from U.S. Pat. No. 5,532,251 (=EP 665,014).
Furthermore, 3-phenylsulfonyl-3,7-diazabicyclo [3.3.1 ]nonane derivatives and medicaments containing them with antiarrhythmic properties are known from U.S. Pat. No. 5,576,327 and 5,635,511 (=EP 665,228).
Despite the efforts of the art, however, there has remained a need for active substances with effective antiarrhythmic activity.
It is an object of the present invention to provide new antiarrhythmic active substances with an improved activity profile.
Furthermore, it is an object of the invention to provide new 3,7-diazabicyclo[3.3.1]nonane compounds having valuable pharmacological properties.
These and other objects are achieved in accordance with the present invention by providing a compound corresponding to the formula I: 
wherein
R1 is an alkyl group with 1-6 carbon atoms or a cycloalkylalkyl group with 4-7 carbon atoms,
R2 is lower alkyl, and
R3 is lower alkyl, or
R2 and R3 together form an alkylene chain with 3-6 carbon atoms, and
R4 represents a phenyl radical monosubstituted in the ortho or para position by nitro, cyano or lower alkanoyl or disubstituted in the ortho and para positions by nitro;
or a physiologically compatible acid addition salt thereof.
It has now been found that the novel 3,7,9,9-tetrasubstituted 3,7-diazabicyclo[3.3.1]nonane compounds bearing a substituted phenyl radical in position 3 possess valuable pharmacological properties for the treatment and/or prophylaxis of cardiac arrhythmias and exhibit an antiarrhythmic action profile which makes them particularly suitable for the treatment of cardiac arrhythmias, in particular tachycardic arrhythmias.
The invention therefore relates to novel compounds of the general formula I 
wherein
R1 is an alkyl group with 1-6 carbon atoms or a cycloalkylalkyl group with 4-7 carbon atoms,
R2 is lower alkyl, and
R3 is lower alkyl, or
R2 and R3 together form an alkylene chain with 3-6 carbon atoms, and
R4 represents a phenyl radical monosubstituted in the ortho or para position by nitro, cyano or lower alkanoyl or disubstituted in the ortho and para position by nitro,
and their physiologically compatible acid addition salts.
If R1 in the compounds of Formula I represents an alkyl group, this may be straight-chain or branched and contain 1 to 6, preferably 3 to 5, in particular 4, carbon atoms. A cycloalkylalkyl group R1 may preferably be cyclopropylmethyl. Alkyl radicals with 3 to 5 carbon atoms have proved particularly suitable radicals R1.
If the substituents R2 and R3 represent lower alkyl, these alkyl groups may be straight-chain or branched and contain 1 to 4, preferably 1 to 3, carbon atoms and in particular represent methyl.
If R2 and R3 together form an alkylene group, this may contain 3 to 6, preferably 4 to 5, carbon atoms. In particular, those compounds in which R2 and R3 together represent an alkylene chain with 4 to 5 carbon atoms have proved suitable.
The substituent R4 represents a substituted phenyl group, in which the substituents of the phenyl group are arranged in the ortho or para position. A lower alkanoyl substituent may contain 2 to 5, preferably 2 to 3, carbon atoms. Preferably R4 represents a phenyl group substituted in the para position by cyano or lower alkanoyl, in particular cyano.
According to the invention, the novel compounds of Formula I and their acid addition salts are obtained by reacting compounds of the general formula II 
wherein R1, R2 and R3 have the above meanings, in known manner with compounds of the general formula III
R4xe2x80x94Xxe2x80x83xe2x80x83III
wherein R4 has the above meaning and X is halogen, and optionally free bases of Formula I are converted into their acid addition salts or the acid addition salts are converted into the free bases of Formula I.
The reaction of the compounds of Formula II with compounds of Formula III can take place in known manner under conventional conditions for the substitution of aromatic halides by amines. In particular chlorine or fluorine are considered as halogens in the compounds of Formula II. The reaction is carried out in an organic solvent which is inert under the reaction conditions, at temperatures between room temperature and the boiling temperature of the reaction mixture. Suitable organic solvents include, for example, ethers, in particular cyclic ethers such as tetrahydrofuran, lower alkanols such as butanol, lower aliphatic ketones such as acetone, dimethyl sulfoxide, dimethyl formamide, aromatic hydrocarbons such as benzene or toluene or mixtures of the above solvents. Advantageously, the reaction may be carried out under basic conditions e.g. in the presence of an at least equivalent amount of a base. Examples of suitable bases include inorganic bases such as alkali metal hydroxides, alkali metal carbonates, alkali metal amides or alkali metal hydrides and organic bases such as tertiary lower alkylamines.
The compounds of Formula I may be isolated from the reaction mixture and purified in a known manner. Acid addition salts can be converted into the free bases in conventional manner, and these may if desired be converted in known manner into pharmacologically compatible acid addition salts.
Suitable pharmacologically acceptable acid addition salts of the compounds of Formula I include, for example, the salts thereof with the usual inorganic acids, e.g. hydrohalic acids, in particular hydrochloric acid, sulfuric acid or phosphoric acids, or with organic acids, for example lower aliphatic mono-, di- or tricarboxylic acids such as maleic acid, fumaric acid, lactic acid, tartaric acid, acetic acid or citric acid, or with sulfonic acids, for example lower alkanesulfonic acids such as methanesulfonic acid or benzenesulfonic acids optionally substituted in the benzene ring by halogen or lower alkyl, such as p-toluenesulfonic acid.
If the substituents R2 and R3 are different in the compounds of Formula I, the compounds contain an asymmetric center and may exist in two optically, active forms or as a racemate. The present invention includes both the racemic mixtures and the optical isomers of these compounds of Formula I. The optically active compounds can be obtained from the racemic mixtures in a known manner by customary separation processes, e.g. by chromatography on chiral separating materials or by fractional crystallisation of suitable salts using optically active acids. Enantiomerically pure compounds can also be prepared by synthesis from corresponding enantiomerically pure starting compounds of Formula II.
The starting compounds of Formula II are known from published German patent application no. DE 26 58 558, U.S. Pat. No. 4,450,112 (=EP 103,833), and U.S. Pat. No. 4,912,113 (=EP 306,871) and/or can be prepared in a known manner by the methods described in these specifications or analogously to the methods described in these specifications.
The starting compounds of Formula III are known and/or can be prepared using known processes or analogously to known processes.
It has now surprisingly been found that the compounds of Formula I according to the invention and their physiologically acceptable acid addition salts have particularly beneficial antiarrhythmic effects. In particular, they exhibit class III antiarrhythmic properties, which cause a prolongation of the QT interval in the ECG and effect prolongation of the effective refractory period in the heart. The compounds have a beneficial activity profile with good compatibility, a long duration of action and such a high selectivity of the antiarrhythmic action with respect to hypotensive properties that in the antiarrhythmically effective dose range a therapeutically undesired effect on the blood pressure does not occur. The compounds are distinguished in that the antiarrhythmic action is particularly highly pronounced under tachycardic conditions. Furthermore, the compounds according to the invention have properties which make it possible to conclude that their antiarrhythmic properties are accompanied by surprisingly slight proarrhythmogenic side-effects.
The antiarrhythmic activity of the compounds can be demonstrated by standard pharmacological test methods. The example numbers given in the test methods for the individual test substances each relate to the preparation examples which follow.
1. Determination of the Minimum Toxic Dose
Male mice each having a weight of 20 to 25 g were administered maximum doses of 300 mg/kg of the test substance p.o. The animals were observed carefully for toxicity symptoms for 3 hours. Additionally all symptoms and deaths were recorded over a period of 72 hours after administration. Concomitant symptoms were likewise observed and recorded. If death or severe toxic symptoms were observed, further mice were administered increasingly lower doses until toxic symptoms no longer occurred. The lowest dose which caused death or severe toxic symptoms is indicated in the following Table A as the minimum toxic dose.
2. In vivo Investigation of the Antiarrhythmic Properties of the Substances under Tachycardic Conditions in Anaesthetised Guinea Pigs.
The effects of the substances on the effective refractory period (=ERP) and the blood pressure on i.v. administration with increased heart rate were investigated on anaesthetised guinea pigs. A bipolar stimulation catheter was inserted into the right ventricle of the animals via a jugular vein under full anaesthesia. The heart rates of the animals were kept at about 150% of their normal heart rates via this catheter by means of electrical stimulation during the entire investigation. A cannula for i.v. administration of the test substances was inserted in the other jugular vein. During the investigation, the systolic and the diastolic arterial blood pressure (=SAP and DAP) were measured in a carotid artery via a pressure gauge (Statham pressure transducer). The test substances were administered i.v. in increasing doses (cumulatively). Before administration of the first dose and in each case 8 minutes after administration of each dose, the ERP was determined by means of a double pulse protocol. The dose at which a prolongation of the ERP to 115% of the starting value was achieved was considered as the effective dose (=ERP-ED115). Effective doses for a hypotensive effect were considered as the dose at which the SAP was decreased to 85% of its starting value (=SAP-ED85), and the dose at which the DAP was decreased to 85% of its starting value (=DAP-ED85).
The results obtained using the method described above are given in the following Table B.
3. In vitro Determination of the Action of the Test Substances on the Functional Refractory Period on Electrically Stimulated Papillary Muscles from Guinea-pig Hearts.
The action of the substances prolonging the refractory period can also be demonstrated in vitro tests by determination of the functional refractory period (=FRP) on the isolated papillary muscle of the right ventricle of guinea pigs.
The heart was quickly removed from guinea pigs which had been sacrificed by a blow to the back of the neck and the papillary muscles of the right ventricle were fixed in organ baths through which temperature-controlled oxygenated nutrient solution flowed. The muscle preparations were electrically stimulated with a frequency of 3 Hz. The test substances were added to the organ baths in increasing concentrations (cumulatively). In each case 20 minutes after addition of the test substance, the functional refractory period was determined by means of a double pulse protocol. In each case a cumulative concentration/action curve was plotted from the measured values. The concentration at which a prolongation of the FRP by 12 milliseconds was achieved was calculated from this as the effective concentration (=FRP-EC+12ms).
The results obtained using the method described above are given in the following Table C.
4. In vitro Determination of the Potential Proarrhythmogenity of the Substances on Isolated Perfused Rabbit Hearts
The extent of the potential proarrhythmogenity of Class III antiarrhythmic substances can be estimated using the measurement of electrophysiological parameters such as xe2x80x9cinstabilityxe2x80x9d and xe2x80x9ctriangulationxe2x80x9d (see below) on the monophasic action potential, derived from isolated perfused rabbit hearts. The pharmacological test set forth below was performed analogously to the method fundamentally described in L. M. Hondeghem et al., Circulation 103 (2001) 2004-2013 (referred to hereafter as xe2x80x9cHondeghem et al.xe2x80x9d), in conjunction with L. M. Hondeghem, Journal of Cardiovascular Electrophysiology 5(8) (1994) 711-721 (referred to hereafter as xe2x80x9cHondeghemxe2x80x9d). The hearts were quickly removed from rabbits which had been sacrificed by a blow to the back of the neck, and were immediately perfused in a Langendorff arrangement under constant pressure (80 cm H2O) with temperature-controlled oxygenated nutrient solution. The heart was stimulated with different stimulation protocols using two stimulation electrodes which were each arranged in the region of the right and left crus of the bundle of His (cf. xe2x80x9cHondeghem et al.xe2x80x9d). Two further electrodes (one discharge electrode endocardially in the region of the septum of the left ventricle and a reference electrode epicardially on the left ventricle) served to discharge the monophasic action potential.
Using the monophasic action potential duration with different repolarisation levels (APD10-90; xe2x80x9cAPD10xe2x80x9d designates the action potential duration until the occurrence of 10% of repolarisation), the following parameters were derived as indicators of the proarrhythmogenity:
(1) Instability: The change in the APD60 from heartbeat to heartbeat is designated xe2x80x9cinstabilityxe2x80x9d. Under control conditions, this value is on average about 7 milliseconds (=ms). Greater deviations from this average value towards a longer duration ( greater than 7 ms) indicate an increased probability of occurrence for proarrhythmias caused by the test substances investigated.
(2) Triangulation: The repolarisation time in ms from APD30 to ADP90 is designated xe2x80x9ctriangulationxe2x80x9d. Under control conditions, this value is usually about 90 ms. A repolarisation time which is prolonged significantly beyond this control value under the influence of a test substance indicates a slower repolarisation process, which in turn may lead to an increased rate of subsequent polarisations (=proarrhythmias).
The results obtained with the method described above on three hearts (n=3) in each case are reproduced in the following Table D.
5. Blocking Action on the Rapid or Slow Delayed Rectifier Potassium Current, xe2x80x9ciKrxe2x80x9d or xe2x80x9ciKsxe2x80x9d, Respectively
The principle of action of what are called class III antiarrhythmic substances (according to Vaughan-Williams) is based on their blocking of various cellular outward potassium currents which participate in repolarisation of the cardiac action potential. This leads to a prolongation of the cardiac refractory period, by means of which cardiac arrhythmias can be prevented. In this case, the proarrhythmogenic risk of class III antiarrhythmic substances depends on which potassium current or which combination of potassium currents is blocked. It is known from the literature that selective iKr-blocking may hold a high proarrhythmogenic risk, whereas the simultaneous blocking of the iKr and iKs is ascribed a clearly reduced proarrhythmogenic risk.
The iKs can be measured selectively in the manner described below: the hearts are quickly removed from anaesthetised dogs and a muscle section from the left ventricle is perfused with collagenase-containing solution via an arterial vessel. The well-dissociated tissue is comminuted and the individualised cardiac muscle cells are investigated electrophysiologically using the xe2x80x9cwhole-cell patch-clampxe2x80x9d method (cf. O. P. Hamill et al., Pflxc3xctgers Archive 391(2) (1981) 85-100): for selective investigation of the blocking action on the iKs, the inward calcium current is blocked by addition of 1 xcexcM nisoldipine (=selective blocker of the inward calcium current), the iKr by addition of 2xcexcM E-4031 (=selective iKr blocker) and the rapid inward sodium current and the transient outward potassium current by a holding potential of xe2x88x9240 mV. The iKs is then determined using the current amplitude immediately after a 5-second pulse protocol of xe2x88x9240 mV holding potential at most +50 mV depolarisation.
The iKr (HERG) can be measured selectively in the manner stated below: to measure the iKr, a cell line (human embryonal kidney cells, HEK293; see e.g. American Tissue Culture Collection (=ATCC) No.: CRL-1573) is used, which is stably transfected with the gene for the iKr (HERG) (cf. Z. Zhou et al., Biophysical Journal 74(1) (1998) 230-241). Since the cells used do not have any further ion currents which would disrupt the measurement, it is possible to dispense with the corresponding additions of channel-blocking substances. The iKr is determined using the current amplitude at xe2x88x9240 mV holding potential immediately after a 500 ms pulse protocol of xe2x88x9275 mV holding potential at most +10 mV depolarisation. That substance concentration at which 50% of the maximum current is blocked (IC50 %) is determined from the inhibitions of the corresponding current at different substance concentrations. The results obtained with the methods described above are reproduced in Table E below:
In a further in vivo test on anaesthetised cats, the compound of Example 4 after administration p.o. and i.v. in each case exhibited a dosage-dependent, clear, long-lasting increase in the fibrillation threshold, which was more marked on the atrium than on the ventricle. Such an atrioselective increase in the fibrillation threshold is an indication that the tested compound has a beneficial action profile with a reduced proarrhythmogenity risk.
The foregoing test results show that the compounds of Formula I possess antiarrhythmic effects and clearly prolong the effective refractory period of the cardiac muscle, and that an effective hypotensive action of the substances occurs only at doses which are considerably higher than the doses which are effective for prolonging the refractory period. The above test results also indicate a connection between the surprisingly low tendency of the substances according to the invention to develop proarrhythmogenic side-effects and their specific profile of the influencing of the different outward-directed potassium currents in heart cells of larger mammals and humans, for example the influencing of the iKr and iKs.
Due to their activity profile described above, the substances are suitable for the suppression or inhibition of tachycardic cardiac arrhythmias and can be used for the prophylaxis and treatment of cardiac arrhythmias in larger mammals and humans. In particular, the substances are suitable for preventing the occurrence of tachyarrhythmias, i.e. arrhythmias which are coupled to an increase in the heart rate.
The doses to be used may vary individually and will naturally vary according to the type of condition to be treated, the substance used and the form of administration. In general, however, medicinal forms with an active substance content of 0.5 to 100 mg per individual dose, in particular 1 to 25 mg per individual dose are suitable for administration to larger mammals, in particular humans.
As therapeutic agents, the compounds of Formula I may be contained with customary pharmaceutical auxiliaries in pharmaceutical preparations such as e.g. tablets, capsules, suppositories or solutions. These galenic formulations can be prepared by known methods using conventional solid or liquid excipients, e.g. lactose, starch or talcum or liquid paraffins, and/or using conventional pharmaceutical auxiliary substances, for example tablet disintegrants, solubilizers or preservatives.